?>V2 



PRODUCTIVITY OF GROiSE POPULATIONS 



suit of the Julv flood. The average number of chicks ])er brood inaluriiig, however, was simi- 

 lar on both plots. On the other hand the percentage of females rearing broods on the con- 

 trolled unit was nearly double that on the unmanaged area (table 91). The same relation- 

 ship prevailed the following two years, though less strong. These data indicate that, during 

 the same year when environmental conditions were uniform over both units, the greater pro- 

 ductivity associated with lower de:isities of the spring population was largely a result of 

 more successful breeding and nesting rather than of greater survi\ al among the chicks. 



TABLE yi. EFFECT OF BREEDING PUI'LIATION REDUCTION ON PER CENT OF 

 FEMALES REARING BROODS AND AVERAGE NLLMBER OF CHICKS 

 PER BROOD MATURING— CONNECTICUT HILL— 1935-1937 



At the same time, however, it has so happened, as shown in table 83, that survival among 

 the chicks on the study areas over the full period of the Investigation has varied inversely 

 with the density of the breeding population. Yet the extent to which this represents cause 

 and effect is not clear. In any event, on Connecticut Hill, it apparently was the weaker in- 

 fluence, on the average, in reducing the productivity of high spring populations, although 

 this does not seem to have been the case on the Adirondack area. 



With respect to the relative roles of breeding failure and nest mortality, lack of suffici- 

 ently precise data makes appraisal difficult*. On Connecticut Hill there seems little doubt 

 that in 1933 both were high. In 1935 and 1936 the former seems to have been high and 

 the latter low, while in 1940 the reverse was the case. In 1912, the other year of especially 

 low productivity, both were average but brood mortality was high. On the .Adirondack area 

 both have been consistently low. 



To sum up, it appears that in the better grouse coverts of i\ew York, supporting as they 

 do higher densities, the increment of young birds little more than equals the number of breed- 

 ers even in years of good productivity. In the more sparsely inhabited .Vtliroiulaik coverts, 

 on the other hand, it has averaged nearly half again as great. Now and then, however, the 

 forces limiting |)ni(hictivity result in virtual failure of this crop. Heyond this, the relative in- 

 crease on a given area tends to vary inversely with the density of the breeding ])opulati<iii. 



Turning to the net productivity experienced from one breeding season to the next, the rec- 

 ords of the Investigation for the two principal study areas are presented in table 92. Here, 

 loo, marked variations between years have been noted. On Connecticut Hill 1930 and 1931 were 

 years of recovery following the period of scarcity in the late '20s and accordingly were as- 

 sociated with the highest ratios recorded. During succeeding vears moderate gains alternated 

 with substantial losses. The trend on the Adirondack area has sliown a similar pattern, al- 



• Sc« Chipler VUI. p. 359. 



